The result is that the heart muscle may not get enough blood - a condition known as ischaemia.

Dye technology

The US researchers used an imaging method in which red blood cells are labelled with dye to look for pumping abnormalities in the heart which are a clear sign of ischaemia.

A total of 196 patients were included in the study, all of whom had 50% narrowing of at least one major artery or a previous heart attack.

The patients were given a psychological stress test in which they were asked to talk for five minutes on an assigned topic.

Abnormalities in the heart's pumping ability were detected in 20% of the patients during the test.

These patients were found to have a 2.8 times higher death rate than those without the abnormalities over the following five years.

Dr David Sheps, from the University of Florida Health Sciences Centre in Gainesville, said: "This adds to a growing body of evidence that links mental stress and bad outcomes in individuals with coronary artery disease."

Other factors

A spokesman for the British Heart Foundation told BBC News Online that recent figures suggest that people with work stress, depression, lack of support or an angry personality may be more at risk of developing coronary heart disease.

He said: "Stress may also cause people to take up poor lifestyle habits such as smoking or eating bad foods.

"There is evidence that for patients who already have heart disease, stress at work or in the home can bring on angina or even, very exceptionally, a heart attack.

"Although the results are interesting and may help explain a link between stress and CHD, it is a small study focusing specifically on heart patients.

"Further research is needed to establish how the body reacts over time in people who have not yet developed CHD."

The findings were published in Circulation: Journal of the American Heart Association.